This page gives technical information about the properties of solid fuels, for more general information and advice, look at the Solid Fuels page.

The composition and calorific values are based on information averaged from official EN Standards, and therefore represents to some extent the 'official' figures, though may not be completely representative of fuels commercially available. Wood Fuel in particular is highly variable.

Typical properties of solid fuels, as supplied

Anthracite

Hard Coke

Soft Coke

Hard Briquettes

Bituminous Coal

Lignite Briquettes

Peat Briquettes

Dry Wood Logs

Wood Pellets

300ºC Charcoal

Dry Baled Wheat Straw

Moisture %

4.5

8.5

8.5

12

7.5

18.5

11.5

18.5

5

2

15

Ash %

8.5

9.5

7

8

5

7.5

5

<1

0.15

3

4

Volatiles %

8.5

1.5

9

11

32.5

56.5

68

84

80

30

72

Hydrogen %

3.5

0.5

2

3

4.5

3.5

5.15

5.5

6

1

5

Carbon %

85

85

80

80

60

52.5

48.5

40

48

67

42

Sulfur %

1

1

1

1

1

2

0.2

0.01

0.01

<0.01

0.2

Siegert number

0.683

0.290

0.290

0.683

0.672

1

0.7

0.650

0.650

...

...

Heat content kJ/kg

31155

27050

28000

29500

26750

19500

18050

18500

18600

26700

16000

* Air required for combustion m³/kg

9.4

8.4

7

7

6.9

5.7

5.7

4.4

4.4

8.4

...

Bulk kg/m³

879

450

410

830

800

720

750

370

650

180

100

Potential Heat kW/kg

8.65

7.51

7.78

8.19

7.43

5.42

5.01

5.14

5.17

7.42

4.44

Bulk Potential kW/m³

7603

3380

3190

6798

5944

3902

3758

1902

3358

1335

444

Auto-ignition temperature ºC

...

400

...

...

300

...

...

270

...

...

...

*Air required for combustion assumes perfect (stoichiometric) mix of fuel and air, in practice this is rare, 2x air is not uncommon. Flue gas emitted (at perfect combustion) is almost exactly the same as the air required for combustion as, although part of the air is absorbed into the ash, this is almost exactly compensated for by the emission of volatiles.